In the past few years, headphones have upped their gadget status. Celebrity endorsements and the greater attention paid to style has encouraged many more "mainstream" buyers to splash out more money on their cans. However, noise cancellation remains something of a niche, limited to expensive on- and over-ears pairs like the Bose QuietComfort 15 and a smattering of relatively unpopular in-ear alternatives.
Cancellation shouldn't be confused with noise isolation, whereby external sound is suppressed simply by either your earphones or headphones being in the way (exceedingly effective though this can be).. In the QuietComfort 15, microphones behind little grilles on the back of each earcup monitor ambient noise. Then, an inverse wave of this noise is passed through the headphones speakers, rendering background noise inert - or cancelling it out.
This ported design makes the Bose QuietComfort 15 leak sound a little more than fully-enclosed headphones, but part of the idea of noise cancellation is that it means you won't have to turn the volume up as high, diminishing the annoyance of folk nearby. Apple earbuds blasting out tinny fuzz these are not.
Bose's noise cancellation is superb. Short of the company having a patent on "good cancellation", we're not quite sure why alternatives like the House of Marley Destiny TTR and Blackbox solutions never seem to quite match up. The Bose QuietComfort 15 headphones decimate all low-end noise. Engine growls and the droney buzz of air conditioning units disappear, making them perfect for use on trains, buses and planes. Just walking along a road, the extent to which they dampen the din of passing cars is quite remarkable.
Noise cancellation is less effective at scrubbing-out sound higher-up the frequency spectrum, though. It won't entirely eliminate people's voices, especially female ones, but it does take the edge off nearby conversations. And perhaps being able to hear people isn't such a bad thing, when the alternative may mean missing your bus/train stop or a free miniature bottle of wine during a trip across the Atlantic.
However, if you're looking for something to block out the noises made by co-habitees or those of a place less afflicted by the modern low-end burble than a city, we'd advise considering the noise isolating option with either IEM or closed-back, over-ears headphones. You're absolutely paying a premium for noise cancellation here, and while it comes with huge benefits, they won't be worth the cost for everyone.
We also advise trying to evaluate noise cancelling before laying-down more than £200. Due to the simple physics involved, the QuietComfort 15 increase pressure in your ear, a sensation that some people find uncomfortable, leading to headaches and nausea. We've suffered from both in the past, but, like most things, you tend to get used to it - generally without revisiting your lunch in the process.
The Bose QuietComfort 15 only output music when noise cancelling is on. Flip the switch on the back of the right ear cup and they go dead completely. As an AAA battery provides up to 35 hours of music, this isn't a huge concern. But these aren't headphones to take on a trailblazing expedition across the Australian outback.